title: The minor groove-binding agent ELB-21 forms multiple interstrand and intrastrand covalent cross-links with duplex DNA and displays potent bactericidal activity against methicillin-resistant Staphylococcus aureus.
abstract: OBJECTIVE
  The antistaphylococcal pyrrolobenzodiazepine dimer ELB-21 forms multiple adducts with duplex DNA through covalent interactions with appropriately spaced guanine residues; it is now known to form interstrand and intrastrand adducts with oligonucleotide sequences of variable length. We determined the DNA sequence preferences of ELB-21 in relation to its capacity to exert a bactericidal effect by damaging DNA.
  
  
  METHODS
  Formation of adducts by ELB-21 and 12- to 14-mer DNA duplexes was investigated using ion-pair reversed phase liquid chromatography and mass spectrometry. Drug-induced changes in gene expression were measured in prophage-free Staphylococcus aureus RN4220 by microarray analysis.
  
  
  RESULTS
  ELB-21 preferentially formed intrastrand adducts with guanines separated by three nucleotide base pairs. Interstrand and intrastrand adducts were formed with duplexes both longer and shorter than the preferred target sequences. ELB-21 elicited rapid bactericidal effects against prophage-carrying and prophage-free S. aureus strains; cell lysis occurred following activation and release of resident prophages. Killing appeared to be due to irreparable damage to bacterial DNA and susceptibility to ELB-21 was governed by the capacity of staphylococci to repair DNA lesions through induction of the SOS DNA damage response mediated by the RecA-LexA pathway.
  
  
  CONCLUSIONS
  The data support the contention that ELB-21 arrests DNA replication, eliciting formation of ssDNA-RecA filaments that inactivate LexA, the SOS repressor, and phage repressors such as Cl, resulting in activation of the DNA damage response and de-repression of resident prophages. Above the MIC threshold, DNA repair is ineffective.
authors.affiliation: School of Pharmacy, University of London, London, UK.
authors.forename: Helena
authors.initials: H
authors.lastname: Rosado
authors.forename: Khondaker M
authors.initials: KM
authors.lastname: Rahman
authors.forename: Eva-Anne
authors.initials: EA
authors.lastname: Feuerbaum
authors.forename: Jason
authors.initials: J
authors.lastname: Hinds
authors.forename: David E
authors.initials: DE
authors.lastname: Thurston
authors.forename: Peter W
authors.initials: PW
authors.lastname: Taylor
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology*; D001569:Benzodiazepines / Q000378:metabolism* / Q000494:pharmacology*; D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism / Q000494:pharmacology; D004260:DNA Repair / Q000187:drug effects; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D046228:Microarray Analysis; D050296:Microbial Viability / Q000187:drug effects*; D011485:Protein Binding; D011758:Pyrroles / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D018736:DNA Adducts; D011758:Pyrroles; C438462:pyrrolo(2,1-c)(1,4)benzodiazepine; D001569:Benzodiazepines; D004247:DNA